1. Field of the Invention
The present invention relates to a drive circuit device.
2. Description of Related Art
In general, a drive circuit (inverter), which includes switching arms connected in parallel, is used to supply driving electric power to an electric motor. Each of the switching arms includes switching elements such as FETs connected in series. As a conventional drive circuit device (motor control device) including the drive circuit, a drive circuit device, which is made small by using a circuit board having a multilayer structure, is known. In the circuit board having the multilayer structure, multiple circuit conductor layers, on which circuit patterns are formed, are stacked with insulating layers being interposed between the circuit conductor layers. For example, see Japanese Patent Application Publication No. 2009-277726.
Since a large drive current for driving the electric motor flows in the drive circuit, the amount of heat generated in the drive circuit is increased, and thus, the drive circuit is likely to be overheated. In the drive circuit device described in Japanese Patent Application Publication No. 2009-277726, switching elements are mounted on one surface of the circuit board and a heat-dissipating unit such as a heat sink is connected to the other surface of the circuit board so that heat is transferred to the heat sink. Accordingly, heat generated in the drive circuit (switching elements) is dissipated efficiently, and thus, the overheat of the drive circuit is prevented.
In recent years, the further reduction of the size of the drive circuit device has been required. However, since a mounting area needs to be secured on the circuit board in the structure in which the switching elements are mounted on one surface of the circuit board as described in Japanese Patent Application Publication No. 2009-277726, there is a limit on the reduction of the size of the drive circuit. Therefore, there has been a demand for development of a new technology that can make the drive circuit device smaller.